Three-dimensional fabrication with cavity filling

ABSTRACT

A three-dimensional printer is configured to fill interior cavities of a fabricated object with functional or aesthetic materials during fabrication. In general, a number of layers can be fabricated with an infill pattern that leaves void space within an exterior surface of the object. These void spaces can receive a second material such as an epoxy or adhesive that spans multiple layers of the object to increase structural integrity. Similarly, aesthetic materials may be used to add color, opacity, or other desired properties to a fabricated object. The void spaces can also or instead form molds that are filled with a build material to provide a fabricated object.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/065,449 filed on Oct. 29 2013, which claims the benefit of U.S. App.No. 61/719,874 filed on Oct. 29, 2012, where the entire content of eachis hereby incorporated by reference.

BACKGROUND

There remains a need three-dimensional printing systems capable offilling interior voids of a fabricated object with aesthetic orfunctional material(s).

SUMMARY

A three-dimensional printer is configured to fill interior cavities of afabricated object with functional or aesthetic materials duringfabrication. In general, a number of layers can be fabricated with aninfill pattern that leaves void space within an exterior surface of theobject. These void spaces can receive a second material such as an epoxyor adhesive that spans multiple layers of the object to increasestructural integrity. Similarly, aesthetic materials may be used to addcolor, opacity or other desired properties to a fabricated object. Thevoid spaces can also or instead form molds that are filled with a buildmaterial to provide a fabricated object.

BRIEF DESCRIPTION OF THE FIGURES

The invention and the following detailed description of certainembodiments thereof may be understood by reference to the followingfigures.

FIG. 1 is a block diagram of a three-dimensional printer.

FIG. 2 depicts an extruder for multiple build materials.

FIG. 3 shows an extrusion head with two extruders.

FIG. 4 illustrates a void-filling process.

FIG. 5 shows a void-closing process.

FIG. 6 shows a layered object with filled voids.

FIG. 7 shows a method for cavity filling.

DETAILED DESCRIPTION

All documents mentioned herein are hereby incorporated in their entiretyby reference. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context. Thus the term “or” should generally beunderstood to mean “and/or” and so forth.

The following description emphasizes three-dimensional printers usingfused deposition modeling or similar techniques where a bead of materialis extruded in a series of two dimensional paths to form athree-dimensional object from a digital model, it will be understoodthat numerous additive fabrication techniques are known in the artincluding without limitation multij et printing, stereolithography,Digital Light Processor (“DLP”) three-dimensional printing, selectivelaser sintering, and so forth. Any such techniques that may benefit fromthe systems and methods described below, and all such printingtechnologies are intended to fall within the scope of this disclosure,and within the scope of terms such as “printer”, “three-dimensionalprinter”, “fabrication system”, and so forth, unless a more specificmeaning is explicitly provided or otherwise clear from the context.

FIG. 1 is a block diagram of a three-dimensional printer. In general,the printer 100 may include a build platform 102, an extruder 106, anx-y-z positioning assembly 108, and a controller 110 that cooperate tofabricate an object 112 within a working volume 114 of the printer 100.

The build platform 102 may include a surface 116 that is rigid andsubstantially planar. The surface 116 may provide a fixed, dimensionallyand positionally stable platform on which to build the object 112. Thebuild platform 102 may include a thermal element 130 that controls thetemperature of the build platform 102 through one or more active devices132, such as resistive elements that convert electrical current intoheat, Peltier effect devices that can create a heating or coolingaffect, or any other thermoelectric heating and/or cooling devices. Thethermal element 130 may be coupled in a communicating relationship withthe controller 110 in order for the controller 110 to controllablyimpart heat to or remove heat from the surface 116 of the build platform102.

The extruder 106 may include a chamber 122 in an interior thereof toreceive a build material. The build material may, for example, includeacrylonitrile butadiene styrene (“ABS”), high-density polyethylene(“HDPL”), polylactic acid (“PLA”), or any other suitable plastic,thermoplastic, or other material that can usefully be extruded to form athree-dimensional object. The extruder 106 may include an extrusion tip124 or other opening that includes an exit port with a circular, oval,slotted or other cross-sectional profile that extrudes build material ina desired cross-sectional shape.

The extruder 106 may include a heater 126 to melt thermoplastic or othermeltable build materials within the chamber 122 for extrusion through anextrusion tip 124 in liquid form. While illustrated in block form, itwill be understood that the heater 126 may include, e.g., coils ofresistive wire wrapped about the extruder 106, one or more heatingblocks with resistive elements to heat the extruder 106 with appliedcurrent, an inductive heater, or any other arrangement of heatingelements suitable for creating heat within the chamber 122 sufficient tomelt the build material for extrusion. The extruder 106 may also orinstead include a motor 128 or the like to push the build material intothe chamber 122 and/or through the extrusion tip 124.

In general operation (and by way of example rather than limitation), abuild material such as ABS plastic in filament form may be fed into thechamber 122 from a spool or the like by the motor 128, melted by theheater 126, and extruded from the extrusion tip 124. By controlling arate of the motor 128, the temperature of the heater 126, and/or otherprocess parameters, the build material may be extruded at a controlledvolumetric rate. It will be understood that a variety of techniques mayalso or instead be employed to deliver build material at a controlledvolumetric rate, which may depend upon the type of build material, thevolumetric rate desired, and any other factors. All such techniques thatmight be suitably adapted to delivery of build material for fabricationof a three-dimensional object are intended to fall within the scope ofthis disclosure.

The x-y-z positioning assembly 108 may generally be adapted tothree-dimensionally position the extruder 106 and the extrusion tip 124within the working volume 114. Thus by controlling the volumetric rateof delivery for the build material and the x, y, z position of theextrusion tip 124, the object 112 may be fabricated in three dimensionsby depositing successive layers of material in two-dimensional patternsderived, for example, from cross-sections of a computer model or othercomputerized representation of the object 112. A variety of arrangementsand techniques are known in the art to achieve controlled linearmovement along one or more axes. The x-y-z positioning assembly 108 may,for example, include a number of stepper motors 109 to independentlycontrol a position of the extruder 106 within the working volume alongeach of an x-axis, a y-axis, and a z-axis. More generally, the x-y-zpositioning assembly 108 may include without limitation variouscombinations of stepper motors, encoded DC motors, gears, belts,pulleys, worm gears, threads, and so forth. For example, in one aspectthe build platform 102 may be coupled to one or more threaded rods sothat the threaded rods can be rotated to provide z-axis positioning ofthe build platform 102 relative to the extruder 124. This arrangementmay advantageously simplify design and improve accuracy by permitting anx-y positioning mechanism for the extruder 124 to be fixed relative to abuild volume. Any such arrangement suitable for controllably positioningthe extruder 106 within the working volume 114 may be adapted to usewith the printer 100 described herein.

In general, this may include moving the extruder 106, or moving thebuild platform 102, or some combination of these. Thus it will beappreciated that any reference to moving an extruder relative to a buildplatform, working volume, or object, is intended to include movement ofthe extruder or movement of the build platform, or both, unless a morespecific meaning is explicitly provided or otherwise clear from thecontext. Still more generally, while an x, y, z coordinate system servesas a convenient basis for positioning within three dimensions, any othercoordinate system or combination of coordinate systems may also orinstead be employed, such as a positional controller and assembly thatoperates according to cylindrical or spherical coordinates.

The controller 110 may be electrically or otherwise coupled in acommunicating relationship with the build platform 102, the x-y-zpositioning assembly 108, and the other various components of theprinter 100. In general, the controller 110 is operable to control thecomponents of the printer 100, such as the build platform 102, the x-y-zpositioning assembly 108, and any other components of the printer 100described herein to fabricate the object 112 from the build material.The controller 110 may include any combination of software and/orprocessing circuitry suitable for controlling the various components ofthe printer 100 described herein including without limitationmicroprocessors, microcontrollers, application-specific integratedcircuits, programmable gate arrays, and any other digital and/or analogcomponents, as well as combinations of the foregoing, along with inputsand outputs for transceiving control signals, drive signals, powersignals, sensor signals, and so forth. In one aspect, this may includecircuitry directly and physically associated with the printer 100 suchas an on-board processor. In another aspect, this may be a processorassociated with a personal computer or other computing device coupled tothe printer 100, e.g., through a wired or wireless connection.Similarly, various functions described herein may be allocated betweenan on-board processor for the printer 100 and a separate computer. Allsuch computing devices and environments are intended to fall within themeaning of the term “controller” or “processor” as used herein, unless adifferent meaning is explicitly provided or otherwise clear from thecontext.

A variety of additional sensors and other components may be usefullyincorporated into the printer 100 described above. These othercomponents are generically depicted as other hardware 134 in FIG. 1, forwhich the positioning and mechanical/electrical interconnections withother elements of the printer 100 will be readily understood andappreciated by one of ordinary skill in the art. The other hardware 134may include a temperature sensor positioned to sense a temperature ofthe surface of the build platform 102, the extruder 126, or any othersystem components. This may, for example, include a thermistor or thelike embedded within or attached below the surface of the build platform102. This may also or instead include an infrared detector or the likedirected at the surface 116 of the build platform 102.

In another aspect, the other hardware 134 may include a sensor to detecta presence of the object 112 at a predetermined location. This mayinclude an optical detector arranged in a beam-breaking configuration tosense the presence of the object 112 at a predetermined location. Thismay also or instead include an imaging device and image processingcircuitry to capture an image of the working volume and to analyze theimage to evaluate a position of the object 112. This sensor may be usedfor example to ensure that the object 112 is removed from the buildplatform 102 prior to beginning a new build on the working surface 116.Thus the sensor may be used to determine whether an object is presentthat should not be, or to detect when an object is absent. The feedbackfrom this sensor may be used by the controller 110 to issue processinginterrupts or otherwise control operation of the printer 100.

The other hardware 134 may also or instead include a heating element(instead of or in addition to the thermal element 130) to heat theworking volume such as a radiant heater or forced hot air heater tomaintain the object 112 at a fixed, elevated temperature throughout abuild, or the other hardware 134 may include a cooling element to coolthe working volume.

In general, the above system can build a three-dimensional object bydepositing lines of build material in successive layers—two-dimensionalpatterns derived from the cross-sections of the three-dimensionalobject. As described below, three-dimensional printing may be augmentedto accommodate multi-material builds.

FIG. 2 depicts an extruder for multiple build materials. In general, anextruder 200 of a three-dimensional printer may include an extrusionhead 202 with a feed 204 and a nozzle 206, along with any suitableheating elements or the like as described above, along with a filamentchanger 208 and a processor such as any of the controllers describedabove.

The filament changer 208 may, for example include a first feed 210 and asecond feed 212 that receive a first build material 214 and a secondbuild material 216 respectively. The filament changer 208 may, forexample slide horizontally over a blade or other cutting edge to cut oneof the build materials 214, 216 that is being moved away from the feed204 of the extruder 200 while moving the other one of the buildmaterials 214, 216 into the feed 204 of the extruder 200. In one aspect,each of the feeds 210, 212 of the filament changer 208 may have anindependent feed drive motor so that the new filament can be fed into adrive motor of the extruder 200 in a controlled manner as a loose end ofthe old filament is driven into the extruder 200. In this manner, anadequate driving force can be maintained for the extrusion process whilethe build material is changing. More generally, the filament changer 208may be configured in any suitable fashion to receive a first filament(such as the first build material 214) and a second filament (such asthe second build material 216) and to selectively deliver one of thesefilaments as a build material to the extruder 200. The filament changer208 may be configured to switch between these supplies of materialwithout interrupting the supply of material to the extruder 200, e.g.,using the sliding structure described above; however it should be notedthat the mechanical details of the filament changer 208 are notimportant, and any configuration capable of changing from one buildmaterial to another without an unrecoverable loss of extrusion from theextruder 200 may be suitable employed.

In a similar manner, the filament changer 208 may be configured toreceive and select among any number of additional build materials (infilaments or other form) for feeding to the extruder 200, and tocontrollably select one of the build materials for extrusion undercontrol of a processor or other control signal source. In otherembodiments, two separate extruders may be alternately positioned alongthe tool path with similar affect.

A processor (not shown) may be configured to control the rate ofdelivery of build material from the extruder 200 and to control aselection of the first filament or the second filament by the filamentchanger 208. The processor may include any of the controllers describedabove. The processor may also control an x-y-z positioning assembly asdescribed above along with the extruder 200 and the filament changer 208to fabricate an object from a three-dimensional model. Where thethree-dimensional model includes an exterior surface with two colors,the processor may control the filament changer 208 to change between twodifferent build materials (e.g., of the two colors) in order toreproduce the two colors on an object fabricated from thethree-dimensional model. Thus the colors from the three-dimensionalmodel may be imparted on an exterior of the object according to thecolors of the three-dimensional model, providing multi-color fabricationcapabilities for the three-dimensional printer.

While color switching is one useful application of the systems andmethods described herein, it will be further appreciated that the sametechniques may be employed to switch between multiple build materialsfor a variety of other reasons. For example, different build materialsmay have different optical properties (opacity, color, finish, etc.),different mechanical properties (elasticity, strength, melting point,etc.), different chemical properties (curing conditions, solubility,etc.), thermal properties (insulation, etc.), electrical properties(conductance, etc.) and so forth, any of which might usefully becombined in an object fabricated from a model. The techniques describedherein may be usefully employed to enable switching of build materialsin any such multi-material models.

In particular, the extruder 200 may be used to switch between a firstmaterial, such as a build material, and a second material, such as avoid-filling material, as generally contemplated below.

FIG. 3 shows an extrusion head with two extruders. In general, a firstextruder 302 may be used to extrude a first material and the secondextruder 304 may be used to extrude a second material. The firstmaterial may be any material suitable for fabricating athree-dimensional object, such as any of the build materials describedabove. The second material may, for example, be any material useful forvoid filling, such as a foam, a resin, an adhesive, an epoxy, a glue,and so forth.

As depicted, the first extruder 302 and the second extruder 304 may bejoined together in a shared extrusion head 300. This configurationadvantageously permits shared control with a common x-y-z positioningassembly such as any of the positioning assemblies described above.However it will be understood that a three-dimensional printer may alsoor instead use extruders with separate positioning assemblies withoutdeparting from the scope of this disclosure.

In another aspect, the second material may be a build material similaror identical to the first material. Thus, in certain aspects, a void maybe filled with an extrudate of build material rather than a specializedadhesive or structural filler. Additionally, although the followingdescription refers generally to a first extruder with a first materialand a second extruder with a second material, it should be clear thatthe first extruder and the second extruder may be the same extruder,and/or that the first material and the second material may be the samematerial (or the same type of material). For example, the first materialand the second material may be a single type of build material, and mayin certain embodiments be extruded alternately from a single extruder.While the first tool 302 may optionally be used to distribute suchfillers, a different tool such as the second tool 304 may advantageouslybe optimized for high volume dispensation (e.g., with a larger extrusionorifice) or otherwise adapted for use with various fill materials havingdifferent properties than typical build materials.

In general, the extrusion head 300 may be controlled by a controllersuch as any of the controllers described above, and may be positioned byan x-y-z positioning assembly under control of the controller tofabricate a three-dimensional object within a build volume of athree-dimensional printer.

FIG. 4 illustrates a void-filling process. An extrusion head 400 such asany of the extrusion heads described above may be switched from a firstextruder 402 for build material to a second extruder 404 for fillmaterial. The fill material 406 may be used to fill a void in an object408 to any desired level of fullness. The fill material may, as notedabove, be any foam, resin, adhesive, epoxy, glue, or the like. The fillmaterial may also be a liquid, which may be left in liquid form, e.g.,for an aesthetic effect, of the fill material may be a liquid that iscurable into a solid form using, e.g., heat, light, time, curing agents,or the like. In another aspect, the fill material may include siliconeor any other gel or the like, which may also or instead be depositedaround an object during fabrication as a support material.

FIG. 5 shows a void-closing process. After a void 502 in an object hasbeen filled with a fill material from a second extruder 504 of a dualextrusion tool head 506, a first extruder 508 may extrude in a path asgenerally indicated by an arrow 510 to enclose the void 502 with a layer512 of build material. In this manner, the fill material may be enclosedwithin the void 502 to fill the corresponding void space within theobject. This general technique may be adapted in a variety of ways asmore generally discussed herein to achieve desired aesthetic andstructural/functional results.

FIG. 6 shows a layered object with filled voids. In general an object600 may be fabricated from a number of layers 602 with a number ofcavities 604 that are filled with a fill material 606. The cavities 604may be created in any suitable shape, such as cylinders parallel withthe z-axis, rectangles or other prismatic shapes, or any other shape orcombination of shapes suitable for interstitial fabrication within anobject to fill cavities 604. The fill material 606 may be a structuralfiller and/or adhesive used to improve strength across laminationboundaries 608, i.e., between adjacent layers 602 of a layeredfabrication. As shown in FIG. 6, these cavities 604 and fill materials606 may be staggered, overlapped, or otherwise positioned atpredetermined locations relative to layer boundaries, object boundaries,and one another to achieve improved strength in a fabricated object. Inparticular, this type of arrangement addresses a characteristic z-axisweakness of certain layered fabrication techniques by providing solidsupport across layer boundaries. This can advantageously mitigatedelamination or similar z-axis structural disruptions in fabricatedobjects.

Although shown as vertical cavities, in one aspect, the edges ofadjacent ones of the layers 602 about the cavities 604 may be offsethorizontally from each other to provide a rough surface to improvebonding with the filler material. As another example, the void may havea roughly circular cross-sectional shape (when viewed from along thez-axis, i.e., from the top), with the circle in each layer offsetrelative to adjacent layers with some regular or irregular verticalpattern such as a vertical V, a sine wave, or any other arrangement thatshifts in the x-y plane from layer to layer, or after some number oflayers (i.e., vertically aligned for some number of layers, and thenshifting for some number of layers, and so forth). More generally acavity 604 may move and change shape or size as it passes from layer tolayer vertically through an object.

FIG. 7 shows a method for cavity filling.

As shown in step 702, the method 700 may begin with fabricating a numberof layers of an object with a three-dimensional printer. The object maybe fabricated with a first material to provide an object having a numberof layers that generally define an exterior surface of the object and aninfill for the object within the exterior surface. The infill mayfurther define one or more void spaces within an interior of the object.This may include space left in the interior by a regular (e.g.,triangular, square, rectangular, hexagonal) or irregular (e.g., randomspace filling) geometry of vertical walls, such as conventionally usedto provide structural integrity for a three-dimensional object, and toprovide supporting structure for top surfaces where needed. In anotheraspect, the regular pattern of the infill may be further modified toprovide additional cavities as contemplated herein. Thus a cavity mayinclude void space within a preexisting infill pattern, or a cavity maybe an additional volume created within the object. In either case, abottom surface may be provided for the cavity in order to control avolume within the object that is filled with a void-filling material.

The first material may be any suitable build material, such as a buildmaterial selected from a group consisting of acrylonitride butadienestyrene (ABS), high-density polyethylene (HDPL), and polylactic acid(PLA), as well as blends of the foregoing and or other materials, aswell as colorants or other additives used for their aesthetic andfunctional properties.

The void space of each cavity may take a variety of shapes, and have avariety of positions within an object. For example, the void space mayinclude a prism extending through the number of layers, such as arectangular prism, a triangular prism, a hexagonal prism, or a circularprism (i.e., a cylinder). Other shapes may also or instead be used foraesthetic affect, such as by using the shape of a brand or logo, or afanciful shape such as a bunny or a teacup. The prism may extendperpendicular to the number of layers, that is, along the z-axis of alayered fabrication process. In another aspect, the prism may passdiagonally through the number of layers at an off angle from the z-axis.

More generally, each cavity may be formed by cross-sectional shapes thatvary from layer to layer in either or both of position and shape. Forexample, the void space may be defined by a closed shape within each ofthe number of layers, where the closed shape in one of the number oflayers has edges offset from at least one other closed shape in anadjacent one of the number of layers. The closed shape in each one ofthe number of layers may offset relative to an adjacent closed shape inan adjacent one of the number of layers using an offset that varies(within the x-y plane of the fabrication process) from layer to layer.The offsets may be arranged in a regular vertical pattern such as asinusoid, a spiral, or a vertical V so that the center of thecross-section moves regularly from layer to layer (within the x-y planeand along the z-axis) according to the regular vertical pattern.

It will also be understood that any number of cavities may be used, andthe void space may include a plurality of prisms or other shapesextending through the number of layers. Similarly, each such prism orother shape may start and stop at any suitable layer of the object, sothat each one of the plurality of prisms has a top and a bottom each ata different layer height than another one of the plurality of prisms.

More generally, a variety of engineering and structural analysistechniques may be usefully employed to select and optimize the position,shape, size, and length of void spaces in the interior of a fabricatedobject. Without limiting the generality of the foregoing, the voids maybe placed and filled to improve overall rigidity (e.g., by filling witha lightweight, rigid foam), to improve layer-to-layer adhesion (e.g., byplacing voids across structural weak points and filling with buildmaterial), or to control the color or opacity of the resulting object.Similarly, liquids may be used to completely or partially fill voids asa novelty, or to control the weight or dynamic balance of the resultingobject.

As shown in step 704, the method may include depositing a secondmaterial within the void space defined by the infill within the exteriorsurface. As noted above, the infill may inherently define void spacethat can be filled with the second material, or the infill may definefurther void spaces within the interior that are shaped and sized forspecific structural or aesthetic results.

The second material may be any of the build materials described above.The second material may also or instead be a structural filler or anaesthetic filler. For example, the second material may be a structuralfiller such as a foam, a resin, an adhesive, an epoxy, or a glue, or anysuitable combination of these. The structural filler may be a curableadhesive or other curable substance. As another example, the secondmaterial may be an aesthetic filler such as a colored filler or anopaque filler used to control light transmitting properties of afabricated object. The filler may also or instead be a liquid used tocontrol light transmitting properties, dynamic balance, weight, or otherproperties of the fabricated object.

As shown in step 706, the method may include fabricating at least oneadditional layer above the number of layers to enclose the secondmaterial within the void space. This may be, for example, a top layer ofthe object that forms an exterior surface of the object afterfabrication, or this may be an interior layer of the object used toenclose the void and contain the second material contained therein. Incertain instances, such as where the second material serves some furtherpurpose, it may be desired to leave the second material exposed on anexterior surface of the fabricated object, in which case the additionallayer may be omitted and the object may be finished without enclosing asurface of the second material.

While the foregoing description emphasizes a technique for filling voidspace within a fabricated three-dimensional object, it will beappreciated that the same method may be used to fabricate a mold that isfilled with a second material to form a fabricated object. Thus in oneaspect, the first material, the “build material,” may be used tofabricate a mold having an interior shape or void space in the form ofan object to be fabricated. This cavity may then be filled with a secondmaterial, nominally the “fill material” discussed above, that serves asthe actual build material by taking the shape of the interior mold andthen curing or otherwise setting to form the fabricated object. In suchembodiments, the nominal “exterior surface” described above is used toform an interior surface of a mold, and the second material fills thisinterior surface to take the shape of a fabricated object. Thus in oneaspect, the “exterior surface” fabricated with a first material may bethe interior surface of a mold, and the second material used to fill avoid may be used to fill this interior surface to create the fabricatedobject.

It will be understood that this becomes a question of terminology. Usingthis mold forming technique, it may be similarly stated that the infillincludes a void space formed as a mold, and that the second material isa build material, such as a curable or settable material that fills thevoid space to take the form of the mold, thereby providing a fabricatedobject that can be released from the mold after the second material hascured or set as appropriate. Regardless of the terms used, it should beclear that the techniques disclosed herein may be employed to provide amolding process that can be used to fabricate a three-dimensionalobject. This approach may be usefully employed for example to mold fooditems. For example, the second material may be a chocolate or similarconfection heated to a liquid state and then poured into the mold formedby the first material to provide a molded chocolate treat.

The methods or processes described above, and steps thereof, may berealized in hardware, software, or any combination of these suitable fora particular application. The hardware may include a general-purposecomputer and/or dedicated computing device. The processes may berealized in one or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors, or otherprogrammable device, along with internal and/or external memory. Theprocesses may also, or instead, be embodied in an application specificintegrated circuit, a programmable gate array, programmable array logic,or any other device or combination of devices that may be configured toprocess electronic signals. It will further be appreciated that one ormore of the processes may be realized as computer executable codecreated using a structured programming language such as C, an objectoriented programming language such as C++, or any other high-level orlow-level programming language (including assembly languages, hardwaredescription languages, and database programming languages andtechnologies) that may be stored, compiled or interpreted to run on oneof the above devices, as well as heterogeneous combinations ofprocessors, processor architectures, or combinations of differenthardware and software.

Thus, in one aspect, each method described above and combinationsthereof may be embodied in computer executable code that, when executingon one or more computing devices, performs the steps thereof. In anotheraspect, the methods may be embodied in systems that perform the stepsthereof, and may be distributed across devices in a number of ways, orall of the functionality may be integrated into a dedicated, standalonedevice or other hardware. In another aspect, means for performing thesteps associated with the processes described above may include any ofthe hardware and/or software described above. All such permutations andcombinations are intended to fall within the scope of the presentdisclosure.

It should further be appreciated that the methods above are provided byway of example. Absent an explicit indication to the contrary, thedisclosed steps may be modified, supplemented, omitted, and/orre-ordered without departing from the scope of this disclosure.

The method steps of the invention(s) described herein are intended toinclude any suitable method of causing such method steps to beperformed, consistent with the patentability of the following claims,unless a different meaning is expressly provided or otherwise clear fromthe context. So for example performing the step of X includes anysuitable method for causing another party such as a remote user or aremote processing resource (e.g., a server or cloud computer) to performthe step of X. Similarly, performing steps X, Y and Z may include anymethod of directing or controlling any combination of such otherindividuals or resources to perform steps X, Y and Z to obtain thebenefit of such steps.

While particular embodiments of the present invention have been shownand described, it will be apparent to those skilled in the art thatvarious changes and modifications in form and details may be madetherein without departing from the spirit and scope of this disclosureand are intended to form a part of the invention as defined by thefollowing claims, which are to be interpreted in the broadest senseallowable by law.

What is claimed is:
 1. A three-dimensional printer comprising: a firstextruder configured to extrude a first build material; a second extruderconfigured to extrude a second build material; and a controller, thecontroller configured to fabricate a number of layers of an object froma computer model using a first material to provide an object having anumber of layers including an exterior surface and an infill within theexterior surface, the controller further configured to deposit a secondmaterial within a void space defined by the infill within the exteriorsurface, and the controller further configured to fabricate at least oneadditional layer above the number of layers based on the computer modelto enclose the second material within the void space.
 2. Thethree-dimensional printer of claim 1, wherein the first extruder and thesecond extruder are a single extruder.
 3. The three-dimensional printerof claim 1, wherein the first material and the second material are asingle type of build material.
 4. The three-dimensional printer of claim1, wherein the void space forms a mold for a three-dimensional objectand the second material includes a build material for thethree-dimensional object.
 5. The three-dimensional printer of claim 1,wherein the infill is formed of a regular geometry.
 6. Thethree-dimensional printer of claim 1, wherein the first material is abuild material selected from a group consisting of acrylonitridebutadiene styrene (ABS), high-density polyethylene (HDPL), andpolylactic acid (PLA).
 7. The three-dimensional printer of claim 1,wherein the second material is a structural filler.
 8. Thethree-dimensional printer of claim 7, wherein the structural filler isone or more of a foam, a resin, an adhesive, an epoxy, and a glue. 9.The three-dimensional printer of claim 7, wherein the structural filleris a curable adhesive.
 10. The three-dimensional printer of claim 1,wherein the second material is an aesthetic filler.
 11. Thethree-dimensional printer of claim 10, wherein the aesthetic filler isone or more of a colored filler and an opaque filler.
 12. Thethree-dimensional printer of claim 10, wherein the aesthetic filler is aliquid.
 13. The three-dimensional printer of claim 12, wherein the voidspace includes a prism extending through the number of layers.
 14. Thethree-dimensional printer of claim 13, wherein the prism includes arectangular prism or a cylinder.
 15. The three-dimensional printer ofclaim 13, wherein the prism is perpendicular to the number of layers.16. The three-dimensional printer of claim 13, wherein the prism passesdiagonally through the number of layers.
 17. The three-dimensionalprinter of claim 1, wherein the void space includes a plurality ofprisms extending through the number of layers, and wherein each one ofthe plurality of prisms has a top and a bottom each at a different layerheight than another one of the plurality of prisms.
 18. Thethree-dimensional printer of claim 1, wherein the void space is definedby a closed shape within each of the number of layers, where the closedshape in one of the number of layers has edges offset from at least oneother closed shape in an adjacent one of the number of layers.
 19. Thethree-dimensional printer of claim 1, wherein a number of offsets for anumber of closed shapes in a number of layers are arranged in a regularvertical pattern.
 20. A computer program product comprising computerexecutable code embodied in a non-transitory computer readable mediumthat, when executing on a three-dimensional printer, performs the stepsof: fabricating a number of layers of an object with thethree-dimensional printer using a first material to provide an objecthaving a number of layers including an exterior surface and an infillwithin the exterior surface; and depositing a second material within avoid space defined by the infill within the exterior surface; andfabricating at least one additional layer above the number of layers toenclose the second material within the void space.